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“Our eventual goal is to use this technique for any type of feedstock, to produce any biofuel or biochemical that can use these sugars,” says Dr. Ratna Sharma-Shivappa.
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Researchers at North Carolina State Univ. have developed a more efficient
technique for producing biofuels from woody plants that significantly reduces
the waste that results from conventional biofuel production techniques. The
technique is a significant step toward creating a commercially viable new
source of biofuels.
“This technique makes the process more efficient and less expensive,” says
Dr. Ratna Sharma-Shivappa, associate professor of biological and agricultural
engineering at NC State and co-author of the research. “The technique could
open the door to making lignin-rich plant matter a commercially viable
feedstock for biofuels, curtailing biofuel’s reliance on staple food crops.”
Traditionally, to make ethanol, butanol, or other biofuels, producers have
used corn, beets or other plant matter that is high in starches or simple
sugars. However, since those crops are also significant staple foods, biofuels
are competing with people for those crops.
However, other forms of biomass—such as switchgrass or inedible corn stalks—can
also be used to make biofuels. But these other crops pose their own problem:
their energy potential is locked away inside the plant’s lignin—the woody,
protective material that provides each plant’s structural support. Breaking
down that lignin to reach the plant’s component carbohydrates is an essential
first step toward making biofuels.
At present, researchers exploring how to create biofuels from this so-called
“woody” material treat the plant matter with harsh chemicals that break it down
into a carbohydrate-rich substance and a liquid waste stream. These
carbohydrates are then exposed to enzymes that turn the carbohydrates into
sugars that can be fermented to make ethanol or butanol.
This technique often results in a significant portion of the plant’s
carbohydrates being siphoned off with the liquid waste stream. Researchers must
either incorporate additional processes to retrieve those carbohydrates, or
lose them altogether.
But now researchers from NC State have developed a new way to free the
carbohydrates from the lignin. By exposing the plant matter to gaseous ozone,
with very little moisture, they are able to produce a carbohydrate-rich solid
with no solid or liquid waste.
“This is more efficient because it degrades the lignin very effectively and
there is little or no loss of the plant’s carbohydrates,” Sharma-Shivappa says.
“The solid can then go directly to the enzymes to produce the sugars necessary
for biofuel production.”
Sharma notes that the process itself is more expensive than using a bath of
harsh chemicals to free the carbohydrates, but is ultimately more
cost-effective because it makes more efficient use of the plant matter.
The researchers have recently received a grant from the Center for Bioenergy
Research and Development to fine-tune the process for use with switchgrass and
miscanthus grass. “Our eventual goal is to use this technique for any type of
feedstock, to produce any biofuel or biochemical that can use these sugars,”
Sharma-Shivappa says.
The research, “Effect of ozonolysis on bioconversion of miscanthus to
bioethanol,” was co-authored by Sharma-Shivappa, NC State Ph.D. student
Anushadevi Panneerselvam, Dr. Praveen Kolar, an assistant professor of
biological and agricultural engineering at NC State, Dr. Thomas Ranney, a
professor of horticultural science at NC State, and Dr. Steve Peretti, an
associate professor of chemical and biomolecular engineering at NC State. The
research is partially funded by the Biofuels Center of North Carolina.
SOURCE
